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1. A valve assembly for a printer ink cartridge, said valve assembly comprising:a flanged valve stem defining an inlet opening with a skirt engaging portion for operatively engaging an outlet port of the cartridge;a depressible valve member within the stem; anda pressure regulator having a spacer within a central hub, a diaphragm spanning a central inlet opening, and a clip defining an outlet opening, the clip configured to operatively engage the valve stem to sandwich the valve member, spacer and diaphragm between the valve stem and clip, the pressure regulator having a spring configured to bias the diaphragm against the central inlet opening into a closed position, so that ink from the ink cartridge is only able to flow through the valve when the diaphragm is in an open position.
2. The valve of claim 1, which includes an ink filter between the valve member and the spacer.
3. The valve of claim 2, wherein ink filter is shaped and dimensioned to extend beyond a radial extent of the valve member so that ink flowing through the valve contacts a relatively large surface area of the filter.
4. The valve of claim 3, which is configured so that hydrostatic pressure of ink in the cartridge acts on an upstream side of the diaphragm, with static ink pressure acting on a downstream side of the regulator outlet opening and the regulator spring, so that while downstream pressure and the spring bias exceeds upstream pressure, the regulator inlet remains sealed against the central hub of the spacer.
5. The valve of claim 4, which is configured so that extraction of ink through the valve lowers hydrostatic pressure of the ink on the downstream side of the diaphragm.
6. The valve of claim 5, which is configured so that when the downstream pressure and the spring bias is less than the upstream pressure, the inlet opening unseats from the central hub to allow ink flow to the regulator outlet enabling fluid pressure equalization on both sides of the diaphragm so that force of the spring increases to re-seal the inlet opening against the central hub.
7. The valve of claim 6, which is configured so that continued extraction of ink through the valve results in the inlet of the pressure regulator successively opening and closing as a pressure difference across the diaphragm oscillates about a threshold pressure difference required to balance a force of the spring.
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